1. Technical Field
The present invention relates to a solid-state imaging device including a solid-state image sensing element having a plurality of photo-transistors that are formed to be linearly arranged.
2. Related Art
A typical example of a conventional solid-state imaging device is described in Japanese Patent Laid-Open No. H6-163,950 (1994). FIG. 7 shows a cross-sectional view along a width direction of a solid-state imaging device described in Japanese Patent Laid-Open No. H6-163,950.
A solid-state imaging device 110 includes an elongated solid-state image sensing element 120 in substantially central portion in a molded case 118, which includes a metallic layer 112 called an “island”. The solid-state image sensing element 120 is mounted on the metallic layer 112. The surface of the solid-state image sensing element 120 is provided with a bonding pad, which is not shown here. A surface of an inner lead 134 is exposed within the molded case 118. The bonding pad is electrically coupled to inner lead 134 through bonding wires 140. Further, the inner lead 134 extends through and beyond the molded case 118 to be coupled to an outer lead 130 outside of the molded case 118. An upper opening of the molded case 118 is encapsulated by a transparent plate 122.
Such type of structure is also described in Japanese Patent Laid-Open No. H7-86,542 (1995), Japanese Patent Laid-Open No. H7-161,954 (1995), Japanese Patent Laid-Open No. H11-330,285 (1997) and Japanese Patent Laid-Open No. 2001-68,578.
Further, Japanese Patent Laid-Open No. 2000-228,475 describes, as shown in FIG. 8, a solid-state imaging device employing a lead frame having a metallic layer 112 of larger dimension in a region right under an amplifier unit of a solid-state image sensing element. It is described that a heat from the amplifier unit of the solid-state image sensing element can be quickly released according to such configuration.
However, the conventional technologies as described above face problems to be solved in the process of releasing heat that has been generated in the amplifier unit of the solid-state image sensing element.
In recent years, a downsizing of a solid-state imaging device is required, and developments for achieving more dense arrangement of pixels and a miniaturization of solid-state image sensing elements are proceeded. Such developments causes an increased amount of heat generated in the amplifier unit of the solid-state image sensing element, leading to an elevated temperature of the solid-state image sensing element and uneven temperature distribution of the pixels. This adversely affects a quality of an image read by the solid-state imaging device, causing a considerable deterioration in the reliability of the solid-state imaging device. Therefore, there is a need in the industry for reducing the temperature of the solid-state image sensing element during the operation by releasing heat from the amplifier unit of the solid-state image sensing element with an improved efficiency to provide an uniform temperature distribution of pixel, thereby achieving a stabilized imaging function of the solid-state image sensing element.
More specifically, the present invention is directed to providing a solution to new and novel issue that is arisen due to a downsizing of solid-state imaging devices, and the issue is solved by achieving an improved efficiency in releasing a heat generated in the amplifier unit of the solid-state image sensing element.